Geothermal heat exchange system for water supply

ABSTRACT

The geothermal heat exchange system for a water supply is an open system, i.e., water flows into the system for consumption and use and is then drained from the system, as opposed to a closed system where the water is recycled through the system. The present system receives water from an elevated source, e.g., a hilltop tank or an elevated community water supply tank, through a relatively large diameter pipe. The water is then delivered to a subsurface pipe system of one or more relatively small diameter pipes for more efficient thermal exchange. The subsurface pipes are preferably manufactured of material having relatively high thermal conductivity. The subsurface pipe system is preferably buried at an intermediate depth between the surface and the depth where constant temperature occurs in order to provide most of the benefits of a subsurface system while reducing the labor required to bury the pipe system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to systems for the heating and cooling of liquids, and particularly to a geothermal heat exchange system for a water supply.

2. Description of the Related Art

Modern plumbing systems universally provide at least for heated water. Many plumbing systems also provide for the cooling of water from ambient temperature. It is well known that the energy expended for heating and cooling the water supply to a dwelling or other building can be quite costly, depending upon the need for water for the particular structure and its occupants. Water has a relatively high specific heat, i.e., water requires a relatively large amount of energy to heat or cool a given amount by a given temperature difference. In such open-ended systems where the water is used for washing or other consumption and then passes to a drain or other outlet, rather than being recycled, the incoming water must be continually heated or cooled, which clearly increases energy needs.

Thus, a geothermal heat exchange system for a water supply solving the aforementioned problems is desired.

SUMMARY OF THE INVENTION

The geothermal heat exchange system for a water supply depends entirely upon gravity flow and ambient subsurface temperature for its operation, and does not consume any other energy. The system is particularly well adapted for supplying water to a relatively small facility, such as a washbasin for washing the hands and/or face, etc. The system draws water from an elevated source, e.g., mountaintop or hilltop supply, elevated community water tank or tower, etc., with the water flowing to a subsurface pipe system (one or more pipes) at a lower elevation than the supply. The subsurface pipe system has sufficient length to retain the water flowing therethrough for sufficient time for the water to be heated or cooled to a temperature substantially equal to that at the level of the pipe system below the surface. The pipe or pipes need not be buried to a depth where the subsurface temperature is constant year round, but may be buried at a shallower depth to reduce the labor involved in the installation of the system. The shallower depth still provides most of the heat exchange benefits that would be achieved at a greater depth. The subsurface pipe or pipes are preferably formed of material having a high thermal conductivity for best thermal exchange.

The supply pipe from the elevated water source has a relatively large diameter, and other below ground pipes and the outlet pipe have considerably smaller diameters. The smaller diameter below ground pipes provide more efficient thermal exchange with the subsurface soil due to their relatively large surface area per their internal volume, as compared to a larger diameter pipe or pipes. The relatively small diameter pipe or pipes also result in a pressure drop when water is flowing therethrough, thereby reducing the pressure head at the plumbing fixture to a practicable level. The subsurface system may comprise a plurality of small diameter pipes in parallel to provide the desired pressure and/or flow, or may comprise a single sinusoidal pipe.

These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevation view of a geothermal heat exchange system for a water supply according to the present invention, showing a first embodiment of the belowground heat exchange plumbing network.

FIG. 2 is a graph illustrating the temperature tread relative to the depth below ground surface, and the preferred or desired depth of the temperature exchange pipes of the geothermal heat exchange system for a water supply according to the present invention.

FIG. 3 is a top plan view of a belowground heat exchange plumbing network for an alterative embodiment of a geothermal heat exchange system for a water supply according to the present invention.

Similar reference characters denote corresponding features consistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The geothermal heat exchange system for a water supply is an open-ended water supply system, i.e., water is supplied from an external source to pass through the system, the water being disposed of as wastewater after it is used. The water passes through a subsurface pipe or network of pipes, where the temperature of the water is adjusted substantially to that of the surrounding earth. The system operates entirely by gravity flow from an elevated external source, so that no pumps or power is required for its operation.

FIG. 1 of the drawings is a schematic illustration of an exemplary geothermal heat exchange system for a water supply according to the present invention. Water is provided from an elevated storage tank or supply 10, e.g., a conventional hilltop or mountaintop water tank, elevated water tower, etc. The water in the tank produces a pressure head 12 relative to the outlet of the system, e.g., a dispensing fixture supply pipe 14, according to the elevation of the tank 10 above the outlet or dispensing fixture supply pipe 14. While the elevated water supply 10 is shown to be directly above the inlet to the geothermal heat exchange system of the present invention in FIG. 1, it should be noted that such water storage tanks are conventionally located at some distance from the end user of the water, and that may be the case with the present system as well. Also, while the present system is entirely dependent upon gravity to supply the required pressure head for water flow, it should be understood that various conventional power means (e.g., pumps, etc.) may be used to fill the elevated storage tank 10.

A relatively large diameter water supply pipe 16 extends downward from the elevated water supply 10 to the surface 18 or ground level. The water supply pipe 16 connects to a subsurface downpipe 20, which, in turn, connects to one or more subsurface heat exchange pipes 22 buried at a predetermined depth below the surface 18. In the example of FIG. 1, a plurality of parallel subsurface water pipes 22 extend from the lower end of the downpipe 20 to a subsurface riser pipe 24. The riser pipe 24 continues above the surface 18 as a dispensing fixture supply pipe 26. The dispensing fixture supply pipe 26 supplies water on demand through a conventional tap or the like (not shown) to its outlet 14 for a dispensing fixture 28, e.g., a wash basin or other fixture as desired. A drain line or pipe 30 removes the wastewater from the fixture 28 to complete the open cycle used in the present system. As the dispensing fixture 28, or more precisely the outlet 14 of the dispensing fixture supply pipe 26, is well below the elevation of the water supply tank 10, the pressure head 12 developed assures that water under pressure will be delivered to the aboveground supply pipe 26 and its outlet 14.

The subsurface water pipes 22 will be seen to have a substantially smaller diameter than the large diameter water supply pipe 16, the downpipe 20, riser pipe 24, and dispensing fixture supply pipe 26 having diameters similar to those of the subsurface pipes 22, although they may have larger diameters. This smaller diameter of the subsurface water pipes 22 results in significantly greater surface area per internal volume of the smaller diameter pipes 22 in comparison to the large diameter water supply pipe 16, which results in more efficient thermal transfer through the subsurface pipes 22 than would be the ease with a larger diameter pipe. Preferably, the large diameter water supply pipe 16 has an inside diameter of about two inches while the smaller diameter subsurface water pipes have inside diameters of about ¾ inch, or a difference of about two and two thirds. This results in the larger diameter water supply pipe having an internal cross-sectional area about seven times greater than the internal cross-sectional areas of the smaller diameter subsurface pipes 22. The relative dimensions are exemplary, and other pipe diameters may be used.

The smaller diameter subsurface water pipes 22 are preferably formed of a highly thermally conductive material, e.g., using a metal alloy of some sort. Copper pipe has high thermal conductivity and serves well as the subsurface water pipe(s) 22 in the present system, although it is more prone to corrosion than some other metals, such as corrosion-resistant steel. Alternatively, a metal having high heat conductivity, such as aluminum, may be used to form the pipe(s) 22, although due care must be taken to minimize corrosion with such a metal. In any event, while non-corrosive plastic pipe may be used, such plastic pipe requires thinner walls, longer pipe runs, and/or more pipes in parallel than is the case with metal pipe.

FIG. 2 of the drawings is a graph representing the relative temperature from the surface to various subsurface depths. It is well known that less variation in the subsurface temperature occurs relative to surface temperature as the subsurface depth increases, until the temperature becomes constant at some point below the surface. This constant temperature depth will vary depending upon the annual temperature extremes of the locale, the type of soil, the ground cover (if any), and perhaps other factors. Accordingly, the chart of FIG. 2 has no specific values, but the principle holds true for all applications. In FIG. 2, point 32 at the surface represents the coldest temperature likely to be experienced in a given locale, i.e., a winter temperature, while point 34 to the right on the surface represents the highest summertime temperature likely to occur. It will be seen that as the subsurface depth increases, both the low and the high temperatures are moderated until at some point 36 below the surface, they meet as the temperature stabilizes to a constant year round value.

As an example of the above, the air temperature at the surface in certain arid climates in the Middle East can range from a high of about 50° Celsius (C.), or about 122° Fahrenheit (F.). Temperatures of objects exposed to the sun may be even warmer, e.g., water in an exposed elevated storage tank. It has been found that the water in such a tank can reach a temperature of up to 60° C., or about 140° F. Winter temperatures at the surface may actually be below freezing at times, on the order of −4° C., or about 25° F. Obviously, some means of mediating such extreme temperatures in a water supply is essential.

It has been found that subsurface temperatures stabilize to a uniform temperature of about 30° C., or about 86° F., at about 5 meters (approximately 16 feet) below the surface in the above-described location. Routing water through a pipe or series of pipes at this depth and allowing the water to take on the temperature of the surrounding subsurface soil will clearly moderate the temperature extremes noted above. However, considerable energy is required to dig to such a depth and remove sufficient earth to allow the placement of a sufficiently large pipe network to provide the desired thermal exchange. If some variation in the water temperature is satisfactory over the seasons of the year, then considerable energy and labor can be saved in the installation of the subsurface thermal exchange pipe network.

Accordingly, the present system provides for the placement of the subsurface thermal exchange water pipes at some intermediate depth between the surface, as represented by points 32 and 34 on the graph of FIG. 2, and the constant temperature depth as represented by point 36 on the FIG. 2 graph. In the Middle East environment described above, it has been found that burying the subsurface water pipe or pipes at a depth of about two meters, or slightly less than seven feet, serves to greatly moderate the temperature of the water at the dispensing fixture supply pipe outlet 14. The winter temperature at such an intermediate depth, as represented by the intermediate point 38 between points 32 and 36 on the graph of FIG. 2, is about 25° C., or about 77° F., while the summer temperature at this intermediate depth, as represented by the intermediate point 40 between points 34 and 36 in FIG. 2, is about 32° C. or about 90° F. While these temperatures are not equal, it will be seen that they are moderated considerably from the surface extremes at those respective times of year, with a year round difference of only about 7° C., or about 13° F. Thus, the placement of the subsurface thermal exchange water pipes at a depth of two meters results in a considerable savings of energy and labor, compared to the work required to dig down to a depth of five meters in order to seek absolutely uniform temperature, and results in acceptable temperature variation for the water that has passed through the system.

The provision of a subsurface water pipe system comprising a plurality of parallel pipes 22 has been illustrated in FIG. 1 and described further above. An alternative subsurface water pipe 42 is illustrated in the top plan view of FIG. 3. In FIG. 3, a large diameter supply pipe 44 is shown in end view. The pipe 44 is connected to a single small diameter subsurface water pipe 42 having a sinusoidal configuration. A small diameter riser pipe 46 extends upward from the outlet end of the sinusoidal subsurface pipe 42. This configuration results in a smaller cross-sectional area through the pipe 42 as compared to the plurality of pipes 22 illustrated in FIG. 1, and to a corresponding reduction in flow. However, it may be suitable for certain installations, such as the single washbasin system of FIG. 1, where a relatively low rate of flow of water is required.

It will be seen that the sinusoidal pipe 42 of FIG. 3 may be bent or otherwise formed of a single length of pipe or, alternatively, it may be assembled of a series of straight lengths, curved sections, elbows, and/or connectors. Moreover, it should be noted that while the term “pipe” has been used to describe the various water conduits used in the present system, the term is not intended to restrict or limit the materials to rigid plumbing pipes and the like. Thin wall tubing and similar materials may be used instead of rigid pipes for the fabrication of any of the geothermal heat exchange systems of the present system, and/or various gauges and wall thickness of pipes and tubing may be mixed.

It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims. 

I claim:
 1. A geothermal heat exchange system for a water supply, comprising: an elevated water supply providing a pressure head; a large diameter water supply pipe extending downward from the elevated water supply; at least one subsurface water pipe disposed below the level of the large diameter water supply pipe, the subsurface water pipe communicating fluidly with the large diameter water supply pipe, the subsurface water pipe being formed of material having a high thermal conductivity; a dispensing fixture water supply pipe communicating fluidly with the at least one subsurface water pipe, the dispensing fixture water supply pipe extending upwardly from the subsurface water pipe to a point above ground level and below the elevated water supply; a dispensing fixture disposed above ground level, the dispensing fixture selectively receiving water from the dispensing fixture water supply pipe; and a wastewater drain extending from the dispensing fixture.
 2. The geothermal heat exchange system for a water supply according to claim 1, wherein: the subsurface water pipe has a smaller diameter than the large diameter water supply pipe; and the dispensing fixture water pipe has a smaller diameter than the large diameter water supply pipe.
 3. The geothermal heat exchange system for a water supply according to claim 1, wherein the subsurface water pipe is buried at an intermediate depth between ground level and a level of constant temperature below ground level.
 4. The geothermal heat exchange system for a water supply according to claim 1, wherein the at least one subsurface water pipe comprises a plurality of small diameter parallel pipes.
 5. The geothermal heat exchange system for a water supply according to claim 1, wherein the at least one subsurface water pipe comprises a single small diameter pipe having a sinusoidal path.
 6. The geothermal heat exchange system for a water supply according to claim 1, wherein the large diameter water supply pipe has a diameter of about two and two-thirds the diameter of the subsurface water pipe.
 7. The geothermal heat exchange system for a water supply according to claim 1, wherein the dispensing fixture is a washbasin.
 8. A geothermal heat exchange system for a water supply, comprising: an elevated water supply providing a pressure head; a large diameter water supply pipe extending downward from the elevated water supply; at least one subsurface water pipe disposed below the level of the large diameter water supply pipe, the subsurface water pipe communicating fluidly with the large diameter water supply pipe, the subsurface water pipe having a smaller diameter than the large diameter water supply pipe; a dispensing fixture water supply pipe communicating fluidly with the at least one subsurface water pipe, the dispensing fixture water supply pipe extending upward from the subsurface water pipe to a point above ground level and below the elevated water supply, the dispensing fixture water pipe having a smaller diameter than the large diameter water supply pipe; a dispensing fixture disposed above ground level, the dispensing fixture selectively receiving water from the dispensing fixture water supply pipe; and a wastewater drain extending from the dispensing fixture.
 9. The geothermal heat exchange system for a water supply according to claim 8, wherein the subsurface water pipe is formed of material having a high thermal conductivity.
 10. The geothermal heat exchange system for a water supply according to claim 8, wherein the subsurface water pipe is buried at an intermediate depth between ground level and a level of constant temperature below ground level.
 11. The geothermal heat exchange system for a water supply according to claim 8, wherein the at least one subsurface water pipe comprises a plurality of small diameter parallel pipes.
 12. The geothermal heat exchange system for a water supply according to claim 8, wherein the at least one subsurface water pipe comprises a single small diameter pipe having a sinusoidal path.
 13. The geothermal heat exchange system for a water supply according to claim 8, wherein the large diameter water supply pipe has a diameter of about two and two-thirds the diameter of the subsurface water pipe.
 14. The geothermal heat exchange system for a water supply according to claim 8, wherein the dispensing fixture is a washbasin.
 15. A geothermal heat exchange system for a water supply, comprising: an elevated water supply providing a pressure head; a large diameter water supply pipe extending downward from the elevated water supply; at least one subsurface water pipe disposed below the level of the large diameter water supply pipe, the subsurface water pipe communicating fluidly with the large diameter water supply pipe, the subsurface water pipe being buried at an intermediate depth between ground level and a level of constant temperature below ground level; a dispensing fixture water supply pipe communicating fluidly with the at least one subsurface water pipe, the dispensing fixture water supply pipe extending upward from the subsurface water pipe to a point above the ground surface and below the elevated water supply; a dispensing fixture disposed above the ground surface, the dispensing fixture selectively receiving water from the dispensing fixture water supply pipe; and a wastewater drain extending from the dispensing fixture.
 16. The geothermal heat exchange system for a water supply according to claim 15, wherein the subsurface water pipe is formed of material having a high thermal conductivity.
 17. The geothermal heat exchange system for a water supply according to claim 15, wherein: the subsurface water pipe has a smaller diameter than the large diameter water supply pipe; and the dispensing fixture water pipe has a smaller diameter than the large diameter water supply pipe.
 18. The geothermal heat exchange system for a water supply according to claim 15, wherein the at least one subsurface water pipe comprises a plurality of small diameter parallel pipes.
 19. The geothermal heat exchange system for a water supply according to claim 15, wherein the at least one subsurface water pipe comprises a single small diameter pipe having a sinusoidal path.
 20. The geothermal heat exchange system for a water supply according to claim 15, wherein the large diameter water supply pipe has a diameter of about two and two-thirds the diameter of the subsurface water pipe. 